Well, while folks get around to checking this thread, a storage expert/guru on this forum that goes by the nic of parsec, recommended that I check out a free hardware monitor app called HWiNFO64 inorder to check if there was a readable sensor for the northbridge on this mobo. Upon downloading and installing this new (well to me) software I set the sensors "on" and got the screen below.
The only line that seemed plausible to be the NB sensor was the one termed "Auxiliary". To the far right is Aida64 which is my mainstay app for monitoring just about everything happening in my system via an OSD panel. You will see that Aida does not detect a temp for the NB so I came to the conclusion that this board did not have one, although it did give me a voltage reading, hmmmm.
Do you remember that you received an app called "ASRock OC Tuner" on a cd that came with the board? I installed it just to see what it was about but left it aside when I came to the conclusion that this mobo was not overclockable precisely because of the hot NB heatsink. What I had forgotten is that you can not only push things up like voltages, multipliers, frequencies, etc., but you can also push them down.
On "CPU NB Voltage", the default is 1.150 v so I started to do an "undervolting" test routine. It is the same as OCing: change a number, run a stress test to see if the OS is stable (I use HeavyLoad Free) for 5 min., push the number to the next level, test and so on until you get a BSOD or a corruption of some type like screen distortions/corruptions. I managed to get it down to .975 v but was rewarded with a BSOD after a minute of testing so I settled on a voltage one step above what you see in the pic: .9875 v., around a 16% reduction from default.
On "mGPU Voltage" it would only go down to 1.10 v so I left it at that (pic shows default voltage 1.15).
The "Auxiliary" reading in HWiNFO64 fluctuates a lot and the stickler is that it will only give a constant reading when on load. When in idle, it will only update every 2-3 min. which is a pain waiting for a new value to show up. However, the min. temp value is way down to 55.5 c when at default it would hoover over 80 c.
In the bios, I see no way to lower the NB voltage to .9875 v. so the downside is that I have to have OC Tuner running or it will default back to 1.150 v. rebooting.
Sooo, if you are not the adventurous, intrepid and curious type (kidding, everyone has a right to be like they are) and are not up to doing a mod to your NB heatsink, this work- around will help lower the temps. I STILL feel the heatsink hot but it might be just enough to get you over the warranty and a bit more. Like I mentioned, I use an external video card so for you that use the IGP (lodged in the NB), underclocking might most probably cause you a world of pain, however give it a shot even if not to the levels I went. Just remember "It's cool to have cool components"!
Good luck and good UVs (undervolts vs. OVs which are tied to OCs which everybody here understands)